Doctor Command

A doctor command (in the style of brew doctor or node --check) iterates over a list of environment preconditions, reports the status of each one, and exits with code 1 as soon as it detects a failure. It is the ideal entry point for new contributors and for CI smoke tests.

The pattern combines process.* and env.* in a sequence of sequential checks. Each check prints [OK], [!] (non-fatal warning), or [X] (failure), and a boolean variable ok accumulates the overall state:

Checks OS, architecture, PID, uptime, memory usage, working directory, HOME, and an optional environment variable. Exits with process.exit(0) if everything is OK or process.exit(1) if any required check fails.

08-doctor.zolo

Playground

// Feature: doctor / diagnostics — self-check script

// Syntax: combines `process.*` + `env.*` + custom checks. Prints

// a readable status and exits with a non-zero code if anything fails.

// When to use: a `myapp doctor` command for new users; CI smoke tests.


use std::process
use std::env

print("=== Zolo doctor ===\n")

var ok = true

// 1. Platform

print("OS:   {env.os()}")
print("ARCH: {env.arch()}")

// 2. PID, uptime, memory.

print("PID:    {process.pid()}")
print("Uptime: {process.uptime()}s")
let mem = process.memory_usage()
print("Memory: rss={mem.rss} bytes")

// 3. Working directory — must be readable.

let cwd, err = process.cwd()
if cwd == nil {
  print("[X] cwd unavailable: {err}")

  ok = false
} else {
  print("[OK] cwd: {cwd}")
}

// 4. HOME defined.

let home = env.home_dir()
if home == nil {
  print("[X] HOME not detected")

  ok = false
} else {
  print("[OK] HOME: {home}")
}

// 5. Required environment variable?

let demo = env.get("ZOLO_DOCTOR_REQUIRED")
if demo == nil {
  // Warning, not failure (tweak to your app).

  print("[!]  ZOLO_DOCTOR_REQUIRED not set (optional)")
} else {
  print("[OK] ZOLO_DOCTOR_REQUIRED = {demo}")
}

print("")
if ok {
  print("status: OK")
  process.exit(0)
} else {
  print("status: FAILED")
  process.exit(1)
}
// expected (healthy):

//   ...checks...

//   status: OK

Requires the Zolo CLI/host — open in the playground or run locally.

Challenge

Add a check that reads env.get("DATABASE_URL") and treats its absence as a failure (not just a warning). Observe how that changes the exit code.